Gain Staging

Unity gain is an important concept in audio. The best signal structure is one where gain is at unity all the way through the chain, until the
channel fader to the mix bus. So, the mic pre steps up the gain, and all other line amps and signal processors neither add nor subtract,
until the fader. This allows you to bypass any processor and really hear what it is doing, and provides the greatest headroom to noise
ratio. This is also the genesis of the term &quot;make-up gain&quot; on compressors. When the circuit is cutting gain by compressing, you add gain back so that the overall effect is unity gain, but with compression.

EQs add and subtract gain but do not always have adjustable make-up gain, so keep this in mind. Of course in the real world, concessions are made to achieve various ends, (like driving one stage harder and cutting the gain in the next stage to drive a compressor or tube circuit harder) but this concept will guide you to excellent signal chains.Learn MoreSee other parts of this manual

Monitoring Gain & Reference Voltages

Meters on VRS8 panel

The input meters in the mixer panel are after the analog input stage, therefore after the gain knob for each channel.

The VRS8 Panel is dBFS scale – meaning the top of the scale is DIGITAL ZERO!

Most of the time you will want your DAW calibrated to 0dB=-18dBFS.

You can use the VRS8 panel to check for clipping above DIGITAL ZERO.

Don’t worry if the meters look lower than you’re used to in your DAW. That’s the dBFS scale. Your DAW is generally calibrated
to make sure you have headroom. The VRS8 panel shows you just how much.

How CMRR works

Summary

Hum

Buzz

Gain

Digital Noise

Thermal Noise (Hiss)

RF

Summary

There is an old rule of thumb to use when connecting gear in your studio that helps prevent ground loops.
It’s been modified here a little to accommodate the modern DAW studio.

Disconnect absolutely everything from absolutely everything. This includes all audio, all USB, all power and power strips, and things
plugged into power strips – Absolutely everything is unplugged. If the question is “can the (whatever) be plugged in?” the answer is no!

As soon as you encounter noise, stop. You have found a ground loop that needs fixing.

Plug one of your speakers into the wall and turn it on. No audio is connected. Is there noise? If no, next step. If yes, call a tech or
electrician.

Plug in the other speaker from that pair. Any noise? If no, move on.

Connect your interface to power, but not your computer. Connect the interface to the first speaker and turn both on. No noise? Great!
Move on.

Connect to the second speaker and turn everything on. No noise? Great! Move on.

Connect the interface to the computer and fire everything up. Connect only necessary computer peripherals like keyboard and mouse –
no powered USB hubs yet! No noise, great!

Run some signal to your interface from the computer and check that the signal is clean.

Now add any additional equipment one piece at a time and check for noise after each one.

When you encounter noise, look for multiple paths to ground. This includes USB cables, audio cables, power cables, etc. Even a
physical connection to another piece of gear, or rack, can cause a loop.

The absolute best way to wire a studio is to use balanced interconnects. Properly used, balanced connections greatly reduce the effect
of ground loops.

Hum

The most common cause of hum is a ground loop.

In modern studios, the computer can often be a source of ground loops – all the grounds are bussed together!

Buzz

The most common cause of buzz (sharper sound than hum) is poor shielding.

Check that all of your cables are balanced and the shield is intact. A simple cable tester will often suffice.

Gain

If you are experiencing issues with gain, let’s check the whole path. Can you isolate where the gain issue is coming from?

Source

This would be the instrument, be it acoustic or electronic or even a human voice

Transmission medium

Air

Wire (analog)

Wire (digital)

Direct Software Connection

Pickup source

Microphone – Be sure to engage phantom power if needed

Analog Line Input

Digital Line Input

Controller on control protocol, like MIDI

Direct Software Connection

Monitor output

This refers to the output after your mix bus or mix output – changes here only affect monitoring and are not printed to the
final mix.

There is sometimes a lot of attenuation or gain at this stage – it can be a source of issues.

If you find yourself adding or subtracting a large amount, check the following:

Check that the Mix Output is reasonable, most would agree that peaks around -18dBFS are standard.

Check that your power amp or speakers that follow the monitor out are calibrated to work with your interface.

If there is a choice of “-10” or “+4,” choose “+4.”

If there is a trim control, adjust it so that there is suitable range. When the monitor fader is around noon,
levels should be clear and present but not too loud to listen.

The VRS8 monitor knob adjusts from -45dB to +7dB from the “MIX OUT” in the VRS8 panel.

Speakers

Are the speakers calibrated correctly?

Is there a problem with the components?

Environment

Excessively or poorly damped rooms can soak up too much sound and “feel quiet” even when the level is loud.

Extraneous noise (audio masking) can be making something seem quiet.

Ears

Are you tired from listening all day?

Are you damaging your hearing?

Amplifier Stages

Preamplifier (“Preamp” or “Pre”) Gain

This is usually the first amplifier stage and is used to raise the source signal to “nominal level.”

Raising the source to “Nominal Level” implies taking a signal of low level (like a mic or direct instrument) and bringing it up to the range of what we would call “Line Level.”

It can also refer to bringing a signal that is above the range of line level, or outside the norms of line level, into the range of “line level

Preamplifier output

Many preamps have an output trim or fader.

Best practice is to have this set around “unity” or no change unless an adjustment is required.

Sometimes this adjustment is necessary if you wish to “drive” the preamp hard but retain “nominal line level” at the output of the preamp. This was often done in original Neve 1073 preamps because the higher gain settings actually switched in another amplifier card and to some people “sounded more Neve-y.” The channel out fader retained the relative nominal level even though the preamp was riding a little higher than would be necessary.

Line input

This refers to the stage after the preamp where the signal is fed line-level into your interface’s DAC.

If you are using the VRS8 mic preamp, this happens internally

If you are using an external line-level source, pathing into the VRS8 Line Input passes you through a variable line-level gain stage that is controlled by the same knob as the preamp.

This could also be the line input of a console, an analog recorder, or any other line input

Signal processing

EQs, compressors and other signal processors can add and subtract level. Best practice is to adjust the processor so that the desired effect is achieved but the processor can be bypassed without a significant change in gain. This is so you can make good decisions about what the processor is doing.

Some signal processors do not feature make-up gain or trim controls. Often times an audio engineer will add another fader or trim control in series with these processors to maintain “unity gain” up until the mix fader.

Signal processing can be “pre-fader” or “post fader,” just like an auxiliary send. The “fader” in this case is the channel fader referred to below.

Channel Fader

The final fader to the Mix Bus is most often where adjustments are made to create the desired “mix” or “balance” of signals. If nominal level and unity gain have been well maintained through the recording process, the channel faders will give you a good visual reference of your relative levels hitting the mix bus. This also gives you the best signal-to-noise (S/N) ratio.

Mix Fader

The Mix fader in general should hover around unity, making small adjustments to achieve your desired mix. Often automation is used here (as well as the channel fader) to make detailed small moves that can greatly impact the mix fader

Mix Insert

Many engineers like to perform some amount of EQ, compression or other processing at the mix bus. The concept of unity gain still applies here – processors should be able to be put in “bypass” without too much change in gain, so you can best judge the processing. Also, the closer you can maintain unity gain, the better your S/N ratio will be.

If you are still having gain issues, contact support at slatesupport.com

Digital Noise

Digital noise often comes from using unbalanced connections in the vicinity of computer equipment, digital audio equipment or switching power supplies.

Be sure that all your critical connections are balanced at both ends.

Thermal Noise (Hiss)

Excessive thermal noise (hiss) may result from poor gain staging – see above

Are you running an outboard preamp into the VRS8 preamp input (XLR pins of the combo jack)? Use the TRS input when connecting
outboard line-level equipment.

RF

RF interference from radio stations often comes from poor shielding, just like buzz.

It can also pop up with ground loops or unbalanced connections.

Poor gain staging can cause this, as the differential signalling used commonly in balanced audio has limits on it’s efficacy.

SLATE DIGITAL

Slate Digital was co-founded in 2008 by Steven Slate and Fabrice Gabriel, with a mission to create the greatest digital audio tools for professional producers, mixers, and engineers.